Valved flash sterilization container

ABSTRACT

A pressure responsive valve assembly for a sterilization container having a valve opening comprises a valve closure member for closing the opening and a fluid tight plenum chamber including a rigid wall and an opposite movable wall connected to the valve closure member for movement along a common axis therewith. A spring biases the movable wall and valve closure member away from the rigid wall of the plenum chamber. The movable wall has an area comparable to that of the valve closure member and the plenum chamber has a relatively small length-to-diameter ratio so that when the valve closure member is moved to open or close the valve, the resulting movement of the chamber movable wall changes the volume of the plenum chamber by less than 20%.

This invention relates to a container for flash sterilization. Itrelates more particularly to an improved valve for such a container.

BACKGROUND OF THE INVENTION

Articles such as medical instruments and the like are usually sterilizedin an autoclave in which the articles are exposed to high pressuresaturated steam for a relatively brief interval. Unless the articles areto be used immediately and in close proximity to the autoclave, it isdesirable to sterilize the articles while they are inside a valvedcontainer as described, for example, in my U.S. Pat. No. 4,748,003.

During the sterilization process, the valves open under the influence ofhigh pressure steam in the autoclave exposing the contents of thecontainer to the hot steam. At the end of the sterilization cycle, whenthe pressure in the autoclave outside the container is returned tonormal, i.e. atmospheric pressure, the valves close so that when thecontainer is removed from the autoclave, the now sterilized articles aremaintained in a completely sealed sterile environment until they areneeded.

The sterilization container described in the above patent has pressureactuated valves in the top and bottom walls of the sterilizationcontainer. Each valve has a large valve opening and a closure therefor,the latter being supported by a bellows capsule mounted inside thecontainer. A return spring mechanism normally maintains the valveclosure in its closed position. However, when the pressure outside thecontainer exceeds that within the container by a few pounds per squareinch, the force on the valve closure exceeds that exerted by the returnspring with the result that the valve closure opens sufficiently toallow high pressure steam to enter the container. That steam collapsesthe bellows which thereupon moves the valve closure to its fully openposition. Both valves being open, high pressure steam can sweep throughthe container and sterilize the articles therein.

When the pressure inside the autoclave returns to normal aftercompletion of the sterilization cycle, the return spring moves the valveclosure of each valve to its closed position thereby sealing thecontainer. As also described in that patent, pressure equalizationoccurs through a special filter member mounted in the container wall sothat a sterile environment at ambient pressure is maintained in thecontainer until the container is opened to remove the articlestherefrom.

While the valve described in the above patent operates satisfactorily,it does have certain drawbacks. First and foremost, the bellows capsulehas a relatively small diameter in relation to the valve opening and alarge length-to-diameter ratio, e.g. 1.3 in./1 in.=1.3. This means thatwhen the valve member starts to open in response to a given pressuredifferential outside and inside the container and the bellows iscollapsed lengthwise, there is a relatively large reduction in thevolume of the bellows, i.e. in excess of 20%, and a correspondinglylarge increase in gas pressure inside the bellows which resists furtheropening of the valve member.

To avoid this problem, the bellows capsule in the prior value has to beevacuated. This necessitates the use of an elaborate return springmechanism in order to overcome the increased back pressure and close thevalve. Also, the requirement for a bellows that must be evacuated makesthe valve somewhat more difficult and expensive to manufacture. Inaddition, sometimes a small leak may develop in the bellows so that airenters the bellows. Resultantly, during the next sterilization cycle,when the valve member begins to open, that air will be compressed,effectively increasing the spring constant of the bellows so that thevalve member does not open as much for a given pressure differentialoutside and inside the container.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the invention to provide a sterilizationcontainer whose valves are rugged, reliable and easy to service.

Another object of the invention is to provide a sterilization containerincorporating valves which can be opened by a minimum pressuredifferential outside and inside the container.

Another object of the invention is to provide a valve for asterilization container which does not include any bellows or otherparts that have to be maintained at a pressure above or belowatmospheric.

A further object of the invention is to provide a valve of this generaltype which has a large valve opening and which opens consistently andquickly in response to a selected small pressure differential across thevalve.

Other objects will, in part, appear hereinafter. The inventionaccordingly comprises the features of construction, combination ofelements and arrangement of parts which will be exemplified in thefollowing detailed description, and the scope of the invention will beindicated in the claims.

Briefly, my sterilization container has large top and bottom openingsthat are closed by pressure-sensitive valves. The valves seal theopenings at normal, i.e. atmospheric, pressure. When the container isplaced in an autoclave and steam is introduced into the autoclave, theincrease in outside pressure causes the valves to open, so that highpressure saturated steam can enter and sweep through the container,flash sterilizing the container contents in the process. When thepressure in the autoclave is reduced at the end of the sterilizationcycle, the valves close thereby sealing the openings so that thecontainer contents will be maintained in a sterile condition until theycan be removed from the container. Each valve in the present containerthus performs the same function as those described in the aforesaidpatent.

The new valve differs, however, in that it incorporates a relativelylarge volume plenum chamber having a movable wall in the form of aspecial, large diameter, flexible, resilient conical diaphragm whichsupports the valve closure member and which helps to maintain thatmember in its closed position when there is no pressure differentialacross the valve. The diaphragm is comparable in area to the areas ofthe valve opening and closure member and the plenum has an effectivelength-to-diameter ratio, which is quite small, i.e. appreciably lessthan 1.

Resultantly, even when the plenum is filled with air at atmosphericpressure, when the diaphragm is deflected as the valve closure memberopens, there is only a relatively small reduction in the total volume ofthe plenum. Indeed, the volume reduction is insufficient to increase thepressure inside the plenum enough to resist or appreciably retardfurther opening of the valve. In other words, in response to a verysmall increase in outside pressure, the valve member opens sufficientlyto expose the large area diaphragm to the high pressure steam. Absentany appreciable opposing force due to increasing back pressure in theplenum, the conical diaphragm inverts and immediately moves the valvemember to its fully open position, allowing high pressure steam to burstthrough the valve opening.

When the pressure outside the container returns to normal, i.e.atmospheric, a relatively small return spring suffices to return thediaphragm and valve member to their original positions, thereby closingthe valve.

The valve is composed of a relatively few components which arerelatively easy and inexpensive to make in quantity. Furthermore, thesecomponents can be assembled quite easily so that assembly andmaintenance costs are kept to a minimum. When installed in asterilization container, the valve provides a very effective andreliable means for exposing the contents of the container to quickbursts of high pressure saturated steam from an autoclave during asterilization cycle and for providing an effective seal followingsterilization so that the interior of the container is maintained in aseptic condition.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description, taken inconnection with the accompanying drawings, in which:

FIG. 1 is an isometric view with parts cut away showing a valvedsterilization container according to this invention;

FIG. 2 is a sectional view on a much larger scale showing in detail apressure actuated valve in the FIG. 1 container, with the valve closuremember being in its closed position;

FIG. 3 is a similar view of the valve, with the valve member in its openposition, and

FIG. 4 is an exploded isometric view showing the various components ofthe container valve.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIGS. 1 and 2 of the drawings, a flash sterilizationcontainer incorporating the invention comprises a bowl 10 and a cover 12for closing the top of the bowl. A suitable seal or gasket (not shown)is provided around the edge of the bowl and/or the edge of the cove toprovide a hermetic seal around the container when the cover is securedto the bowl by means of the locking clips 14.

Cover 12 has a central mesa 12a provided with a relatively largediameter circular opening 16. A gasket 18 extending around the perimeterof opening 16 at the underside of cover 12 functions as a valve seat fora valve closure member 20. Member 20 is shaped, more or less, like acymbal and it has a flat peripheral margin 26a which is arranged to seatagainst gasket 18. The valve member has a diameter which is somewhatlarger than that of opening 16, 3.5 inches in this example, so that themember can effectively close the opening.

Valve member 20 is part of a pressure responsive valve assembly showngenerally at 22 which is supported inside cover 12 opposite opening 16by a generally U-shaped bracket 26. Bracket 26 engages under theassembly and the ends of the bracket legs are turned outward to formflanges 26a. The bracket is suitably secured to cover 12 at oppositesides of opening 16 such as by threaded fasteners 28 which extendthrough registering openings in the cover and flanges and are threadedinto nuts 30.

Referring to FIGS. 2 and 4 of the drawings, valve assembly 22 comprisesa rigid cup 34 which is in the order of 3 inches in diameter and 1 inchdeep. The cup is formed with an enlargement 34a that extends all aroundthe cup at the rim thereof. Also, a central pedestal 36 projects up froma central foundation boss 36a at the bottom wall of cup 34 to locate anupstanding coil spring 38 within the cup.

The open top of cup 34 is closed by a movable wall in the form of aflexible, resilient diaphragm 42. Preferably, the diaphragm is cuppedtoward valve member 20. The illustrated diaphragm has a relatively flatcentral area 42a and a relatively large conical portion 42b whichextends from area 42a to a depending skirt 42c which tightly encirclesthe upper portion of the cup 34 side wall, including the enlargement34a.

A cylindrical channel 42d is formed in the inside surface of skirt 42c.This channel interfits with the enlargement 34a at the rim of cup 34 sothat when the diaphragm is engaged over the cup as shown in FIG. 2, afluid tight seal is established between the diaphragm and the cup allaround the rim of the cup. Preferably, a non-extensible ring 44 is slidover the diaphragm 42 so that it tightly encircles the diaphragm skirt42c to lock the diaphragm to the side wall of cup 34. A peripheralflange 42e at the bottom of the diaphragm skirt 42c provides a positiveseat for the ring 44.

Still referring to FIGS. 2 and 4, diaphragm 42 is formed with anintegral raised deformable button 44 at its central area 42a. Thisbutton is received in a central opening 46 in valve member 20 toflexibly secure that member to the diaphragm. If it becomes necessary toseparate member 20 from the diaphragm, this can be done by deforming thebutton and forcing it back through opening 46.

A locating hole 48 is formed in the underside of the diaphragm portion42a at the center thereof for locating a depending post 52. Post 52 hasan end boss 52a which seats in hole 48 to center the post on thediaphragm central axis. A passage 54 extending in from the opposite orlower end of post 52 receives the upper end of spring 38 so that thepost can telescope onto pedestal 36 thus capturing the spring. Spring 38biases post 52, diaphragm portion 42a and valve closure member 20upwards so that the edge margin 20a of the valve member is urged to seatagainst the gasket 18 encircling valve opening 16, as shown in FIG. 2.

In order to prevent objects from entering valve opening 16 and possiblyinterfering with the proper operation of the valve, a perforated plate58 is secured to the top of mesa 12a by fasteners 28 and nuts 30 or byother suitable means. The perforations 58a in plate 58 should berelatively large and numerous enough so that air and steam can flowfreely through the plate.

Preferably for reasons to be discussed later, the pedestal 33, includingits foundation boss 36a, is provided with an axial passage 62 as shownin FIGS. 2 and 4. The outer or lower end segment of that passage in boss36a is counterbored and threaded at 62a to receive a thumb screw 64. AnO-ring 66 encircles the reduced diameter inner end 64a of the thumbscrew 64 so that when the thumb screw is turned down into counterbore62a, a fluid-tight seal is provided at the bottom of the counterbore.

When valve assembly 22 is assembled as shown in FIG. 2, it defines alarge volume plenum 68 between cup 34 and diaphragm 42, having alength-to-diameter ratio appreciably less than 1, i.e. 1 in./3 in.=0.33in the illustrated valve assembly. When the diaphragm is properly seatedon the cup and the thumb screw 64 is tightened, the plenum isessentially hermetically sealed. Normally, when a gas, i.e. air, withinthe plenum is near ambient temperature (i.e. 50° to 100° F.), thepressure within the plenum is approximately atmospheric pressure. Thiscondition can be assured simply by loosening the thumb screw 64 andventing the plenum to room air.

With atmospheric pressure in the plenum chamber 68, the valve closuremember 20 is urged against its seat at gasket 18 by the spring 38 whichis chosen to provide a force in the order of 1 to 3 lbs. when the valvemember 20 is in its closed position and there is no pressuredifferential across diaphragm 42. The resilient diaphragm itself mayexert an additional small closing force due to some deflection of itsconical portion 42b.

When the container is placed in an autoclave and saturated steam at arelatively high pressure, (e.g. 30 psi), is introduced into theautoclave, the pressure differential across valve member 20 will causethe valve to open slightly. Resultantly, diaphragm 42 becomes exposed tothe full pressure of that steam which is substantially greater than thepressure inside plenum 68 which, as noted previously, is normallyatmospheric pressure. The pressure differential across diaphragm 42causes the diaphragm to immediately invert which motion drives the valvemember 20 to its fully open position shown in FIG. 3. The opening forceis due not only to the aforesaid pressure differential on the diaphragm42, but also the inverting force arising because of the shape of theconical diaphragm itself.

In the illustrated valve embodiment, the valve member 20, when opening,may move a distance in the order of 0.4 inch. However, due to the largediameter of the diaphragm 42, i.e. about 3 inches, and the smalllength-to-diameter ratio of plenum 68 as a whole, i.e. about 0.33, thisresults in a volume decrease of the plenum 68 of less than 20%, i.e.only about 17% in the illustrated valve. This minimizing of the changein the volume of the plenum chamber minimizes the change in the plenumpressure and thus in the external pressure required to open the valve.Typically, an external pressure increase in the order of only 3 to 4 psiis needed to cause valve member 20 to be moved to its fully openposition shown in FIG. 3.

After prolonged operation of valve assembly 22, after it has beensubjected to repeated sterilization cycles, the gas pressure in plenumchamber 68 may become lower than atmospheric pressure due to a slightporosity of the diaphragm 42 material. If the pressure within the plenumbecomes sufficiently low, it may inhibit diaphragm 42 from returning toits fully extended position shown in FIG. 2. Resultantly, following asterilization cycle, the valve closure member 20 may not reach its fullyclosed position against gasket 18 so that the sterile environment insidethe container may be compromised. To avoid this potential problem, atrecommended intervals, the user may loosen the thumb screw 64 to ventplenum chamber 68 to room air.

A similar procedure may be followed if the container undergoes severalsterilization cycles in a short period of time. In this event, thetemperature of the air in the plenum may be increased sufficiently toraise the air pressure appreciably above atmospheric pressure when thevalve member 20 is in its closed position. This will increase the amountof external pressure required to open the valve. Venting the plenum fromtime to time by momentarily loosening thumb screw 64 will avoid thispotential problem.

As shown in FIGS. 2 and 4, the components of valve assembly 22 may berelatively simple stamped metal or molded plastic parts which can bemade easily in quantity at relatively low cost. The cup 34, ring 44,post 52 and thumb screw 64 may be molded of a suitable relatively rigid,heat-resistant, medical grade plastic material. The valve member 20 maybe stamped of metal, e.g. stainless steel, or the aforesaid plasticmaterial, and the diaphragm 42 may be molded of a suitable flexible,resilient heat-resistant, medical grade, plastic material such assilicone rubber. The remaining parts of the assembly, such as spring 38and gaskets 18 and 66, are more or less standard off-the-shelf items.

To assemble the various components of the valve, spring 38 is placed onthe cup pedestal 36 and post 52 is engaged over the spring and pedestal.Next, the diagram 42 is engaged over cup 34 so that the post boss 52aengages in the locating hole 48 of the diaphragm and the diaphragm skirt42c is forced down around the side wall of the cup until the skirtchannel 42d interlocks with the cup enlargement 34a. Then, the lockingring 44 is slipped over the upper end of the diaphragm and engagedaround skirt 42c so that it seats on the diaphragm flange 42e. Finally,the valve closure member 20 is secured to the diaphragm by inserting thediaphragm button 44 through the central opening 46 in member 20. Then,after screwing thumb screw 64 into counterbore 62a of cup 34, bracket 26is engaged under valve assembly 22. A clearance hole 68 is provided inthe bracket to accommodate the boss 36a and to fix the relativepositions of the cup 34 and bracket. Finally, the bracket is secured tocover 12 by means of the threaded fasteners 28 and nuts 30 or by othersuitable means.

If it becomes necessary to clean, repair or replace one or another ofthe assembly components, this can be done quickly and easily byreversing the above procedure. Therefore, such repair and maintenanceshould cause only minimal downtime of the associated container.

It will thus be seen that the objects set forth above, among those madeapparent from the preceding description, are efficiently attained, and,since certain changes may be made in the above construction withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

It is also to be understood that the following claims are intended tocover all of the generic and specific features of the invention hereindescribed.

I claim:
 1. In a valved sterilization container of the type including arelatively large valve opening in a wall of the container and a pressureresponsive valve assembly having a valve closure member with a centralaxis, the improvement wherein the valve assembly comprisesa fluid tightplenum chamber having a movable wall facing the valve closure member,said plenum chamber having an area perpendicular to said axis which iscomparable to the area of the valve closure member, a length-to-diameterratio appreciably less than 1 and an internal pressure not appreciablyabove the pressure outside the chamber; means for connecting togetherthe valve closure member and chamber movable wall so that they aremovable along said axis, said valve closure member being movable betweena closed position in which said valve closure member closes said openingand a fully open position in which the valve closure member does notocclude said opening, and biasing means for urging the valve closuremember toward said closed position, whereby movements of the valveclosure member between its closed and fully open positions in responseto pressure changes across the valve, changes the volume of the plenumchamber by less than 20%.
 2. The container defined in claim 1 whereinthe plenum chamber is generally cylindrical and the valve closure memberand valve opening are circular.
 3. The container defined in claim 1wherein said movable plenum chamber wall comprises a flexible diaphragm.4. The container defined in claim 3 wherein said diaphragm isresiliently cupped toward said valve closure member.
 5. The containerdefined in claim 1 and further including means for selectively ventingthe plenum chamber to the atmosphere.
 6. The container defined in claim5 wherein the venting means comprisemeans defining an opening into theplenum chamber, and releasable closure means for closing said opening.7. A pressure responsive valve assembly for a sterilization container ofthe type having a valve opening, said valve assembly comprisingagenerally cylindrical, fluid tight plenum chamber, said chamber having arigid wall, a discoid movable wall spaced opposite the rigid wall, alength-to-diameter ratio appreciably less than 1 and an internalpressure that is not appreciably above the pressure outside the chamber;a discoid valve closure member for closing said opening, said closuremember having a diameter similar to that of said movable wall; means forconnecting together the valve closure member and movable wall so thatthe valve closure member and movable wall are movable along a commonaxis, and biasing means for urging said valve member and movable wallalong said axis away from the rigid wall of the plenum chamber.
 8. Thevalve assembly defined in claim 7 wherein said movable wall is aflexible diaphragm.
 9. The valve assembly defined in claim 8 whereinsaid diaphragm is resiliently cupped toward said valve closure memberand inverts when moved toward the rigid wall of the plenum chamber. 10.The valve assembly defined in claim 9 wherein said diaphragm includes aconical segment.
 11. The valve assembly defined in claim 9 wherein saidvalve closure member is cupped toward said diaphragm so that it nests insaid diaphragm when the diaphragm inverts.
 12. The valve assemblydefined in claim 7 and further including means for selectively ventingthe plenum chamber to the atmosphere.
 13. The valve assembly defined inclaim 7 wherein said plenum chamber comprisesa rigid, generallycylindrical cup whose bottom wall constitutes said rigid wall and havinga rim, and a flexible resilient diaphragm constituting said movablewall, said diaphragm having a peripheral skirt which snugly engagesaround said rim to provide a fluid tight seal between the cup and thediaphragm.
 14. The valve assembly defined in claim 13 and furtherincluding plenum chamber venting means mounted in a wall of said cup.15. The valve assembly defined in claim 13 wherein the area of thediaphragm is similar to that of the valve closure member.
 16. The valveassembly defined in claim 7 wherein the biasing means comprise a springcompressed between the rigid and movable walls of the plenum chamber.17. A valved sterilization container of the type including a relativelylarge valve opening in a wall of the container and a pressure-responsivevalve assembly having a valve closure member with a central axis, theimprovement wherein the valve assembly comprises;a fluid-tight plenumchamber having a movable wall facing the valve member in the form of aflexible, conical diaphram which is resiliently cupped toward said valveclosure member and which inverts when said valve closure member is movedto its fully opened position, said plenum chamber having an area ofperpendicular to said axis which is comparable to the area of the valveclosure member and a length-to-diameter ratio appreciably less than 1;means for connecting together the valve closure member and diaphram sothat they are movable along said axis, said valve closure member beingmovable between a closed position in which said valve closure membercloses said opening and a fully open position in which the valve closuremember does not occlude said opening, and biasing means for urging thevalve closure member toward said closed position, whereby movements ofthe valve closure member between its closed and fully opened positionsin response to pressure changes across the valve change the volume ofthe plenum chamber by less than 20%.
 18. The container defined in claim17 wherein said valve closure member is cupped in the opposite sensefrom the diaphragm so that it nests in the diaphragm when in its fullyopen position.
 19. A pressure responsive valve assembly for asterilization containder having a valve opening, said valve assemblycomprisinga valve closure member for closing said opening; a generallycylindrical, fluid-tight plenum chamber having a length-to-diameterratio appreciably less than 1, said chamber includinga rigid, generallycylindrical cup having a bottom wall and a rim, and a flexible resilientdiaphram spaced opposite said bottom wall and having a peripheral skirtwhich snugly engages around said rim to provide a fluid-tight sealbetween the cup and the diaphram, means for connecting together thevalve closure member and diaphram so that the valve closure member anddiaphram are movable along a common axis; biasing means for urging saidvalve member and diaphram along said axis away from said cup bottomwall, and a locking ring snugly engaged around said skirt.
 20. Apressure-responsive valve assembly for a sterilization containder havinga valve opening, said valve assembly comprisinga valve closure memberfor closing said opening; a generally cylindrical, fluid-tight plenumchamber having a length-to-diameter ratio appreciably less than 1, saidchamber includinga rigid, generally cylindrical cup having a bottom walland a rim, and a flexible resilient diaphram spaced opposite said bottomwall and having a peripheral skirt which snugly engages around said rimto provide a fluid-tight seal between the cup and the diaphram, meansfor connecting together the valve closure member and diaphram so thatthe valve closure member and diaphram are movable along a common axis,said connecting means including an integral raised projection at thecenter of the diaphram and an opening at the center of the valve closuremember which interfits with said projection, and biasing means forurging said valve closure member and diaphram along said axis away fromsaid cup bottom wall.